The general methodology of a loosely-coupled inertial navigation system (INS) implements two steps for determining estimates of the navigation state vector of a body: (1) propagation of the navigation state vector via numerical (or other) integration of sensed accelerations and rates of the body, and (2) updates (or corrections) to the navigation state vector using external aiding sources. The external aiding source may be one or more of a wide variety of sources, the most common being satellite based navigation systems such as, for example, the USA's global positioning system (GPS). Such INS solutions are used for vehicle navigation, whether they are ground, air, space, or sea going vehicles. Sometimes, however, external aiding sources, such as GPS may become unavailable due to various reasons. For example, GPS may be jammed or may become unavailable due to location.
One possible way to overcome the unavailability of external aiding sources such as GPS includes traditional navigation by image processing. Traditional navigation by image processing registers the location of a newly detected image with respect to a known, stored image. Upon such successful geo-registration, the North, East, and Down (NED) coordinates of the image location may be used as an external aiding source to update the INS derived navigation state vector. Such image based geo-registration typically requires, however, a very powerful computer processing unit (CPU) since real-time geo-registration is very CPU intensive. Use of a very powerful CPU may be prohibitively expensive or may require space unavailable for certain applications.
As a result of the above-mentioned drawbacks, it may be desirable to provide a navigation system that enables a vehicle carrying such a system to obtain a continuous navigation solution, even in conditions where NED external aiding sources such as GPS become unavailable. Furthermore, it may be desirable to provide a navigation system that does not require a powerful CPU.
There may exist a desire to overcome one or more of the above-mentioned drawbacks. The exemplary disclosed systems and methods may seek to satisfy one or more of the above-mentioned drawbacks. Although the presently disclosed systems and methods may obviate one or more of the above-mentioned drawbacks, it should be understood that some aspects of the disclosed systems and methods might not necessarily obviate them.